Mammography rates for breast cancer screening: a comparison of First Nations women and all other women living in Manitoba, Canada, 1999-2008.

Introduction: First Nations (FN) women historically have low rates of preventive care, including breast cancer screening. We describe the frequency of breast cancer screening among FN women living in Manitoba and all other Manitoba (AOM) women after the introduction of a provincial, organized breast screening program and explore how age, area of residence, and time period influenced breast cancer screening participation.

Methods: The federal Indian Registry was linked to 2 population-based, provincial data sources.

Trends in time to diagnosis of colon cancer and impact on clinical outcomes.

Background: There has been a rapid increase in screening for colorectal cancer (CRC) over the past several years in North America. This could paradoxically lead to worsening outcomes if the system is not adapted to deal with the increased demand. For example, this could create increased wait times for endoscopy and delayed time to CRC diagnosis, which could worsen clinical outcomes such as stage at diagnosis and⁄or survival.

Factors associated with physical activity among Canadian high school students.

Objectives: Identifying multi-level factors affecting physical activity (PA) levels among adolescents is essential to increasing activity to promote health within this population. This study examines the associations between PA and 11 independent factors among Manitoba high school students.

Methods: The sample included 31,202 grade 9-12 students who completed the Manitoba Youth Health Survey.

Long-term outcomes following hepatic resection and radiofrequency ablation of colorectal liver metastases.

Recently some have called for randomized controlled trials comparing RFA to hepatic resection, particularly for patients with only a few small metastases. The objectives were to compare local recurrence and survival following RFA and hepatic resection for colorectal liver metastases. This was a retrospective review of open RFA and hepatic resection for colorectal liver metastases between January 1998 and May 2007.

A comparative study of robust tests for spread: asymmetric trimming strategies.

We examined 633 procedures that can be used to compare the variability of scores across independent groups. The procedures, except for one, were modifications of the procedures suggested by Levene (1960) and O'Brien (1981). We modified their procedures by substituting robust measures of the typical score and variability, rather than relying on classical estimators.

Adaptive robust estimation and testing.

We examined nine adaptive methods of trimming, that is, methods that empirically determine when data should be trimmed and the amount to be trimmed from the tails of the empirical distribution. Over the 240 empirical values collected for each method investigated, in which we varied the total percentage of data trimmed, sample size, degree of variance heterogeneity, pairing of variances and group sizes, and population shape, one method resulted in exceptionally good control of Type I errors. However, under less extreme cases of non-normality and variance heterogeneity a number of methods exhibited reasonably good Type I error control.

Canadian breast cancer guidelines: have they made a difference?

Background: A principal objective of the Canadian Clinical Practice Guidelines for the Care and Treatment of Breast Cancer was to reduce the variation in the way that breast cancer was being treated. To evaluate whether this goal has been reached, we examined variations among surgeons for 4 measures of surgical care and tested for differences in province-wide rates and in variations among surgeons before and after the guidelines were released.

Methods: We studied a population-based cohort of 7022 women living in Manitoba in whom breast cancer was diagnosed from 1995 to 2003 inclusive.

Comparing measures of the 'typical' score across treatment groups.

Researchers can adopt one of many different measures of central tendency to examine the effect of a treatment variable across groups. These include least squares means, trimmed means, M-estimators and medians. In addition, some methods begin with a preliminary test to determine the shapes of distributions before adopting a particular estimator of the typical score.

The new and improved two-sample T test.

This article considers the problem of comparing two independent groups in terms of some measure of location. It is well known that with Student's two-independent-sample t test, the actual level of significance can be well above or below the nominal level, confidence intervals can have inaccurate probability coverage, and power can be low relative to other methods. A solution to deal with heterogeneity is Welch's (1938) test.